Method of manufacturing composite foamed resin caskets



Oct. 15, 1968 L. F. CENEGY 3,406,229

METHOD OF MANUFACTURING COMPOSITE FOAMED RESIN GASKETS Original Filed March 9, 1962 3 Sheets-Sheet 1 INVENTOR.

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METHOD OF MANUFACTURING COMPOSITE FOAMED RESIN GASKETS Original Filed March 1962 3 Sheets-Sheet 2 JNVENTOR.

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METHOD OF MANUFACTURING COMPOSITE FOAMED RESIN GASKETS Original Filed March 9, 1962 5 Sheets-Sheet 3 .INVENTOR. .1 0141/5 @fene BY F d/MM United States Patent F METHOD OF MANUFACTURING COMPOSITE FOAMED RESIN CASKETS Louis F. Cenegy, Downey, Calif., assignor to Hitc'o, a corporation of California Original application Mar. 9, 1962,'Ser. 'No."178,617, now Patent No. 3,283,386, dated Nov. 8, 1966. Divided and this application Oct. 23, 1965, Ser. No. 565,328

2 Claims. (Cl. 264-45) This is a division of application Ser. No. 178,617, filed Mar. 9, 1962, now Patent No. 3,283,386.

This invention relates to improved methods of fabricating casket units and more particularly to especially versatile casket units.

Despite the long need for and use of casket materials and structures, there have not heretofore been provided casket materials and structures which satisfactorily met all of the many requirements imposed on them. Obviously it is most desirable that a casket, which serves as the receptacle for the body of a deceased during the funeral and attendant ceremonies, present a dignified and impressive appearance. Such an appearance must be achieved at low cost, however, if the casket is to have widespread use. If the casket is to be used for interment, then a material and construction are desired which can provide a hermetic seal against an underground environment and which can maintain such a seal substantially indefinitely without corrosion or deterioration. On the other hand, if the casket is to be used for cremation, then a casket material is desired which burns readily and with a minimum of residue.

A number of other casket features are desired by the mortician or funeral director. Individual tastes vary as to the display of a deceased, and these variations should be satisfied with aminimum number of basic arrangements. At present it is known to use difi'erent types of casket lids to meet individual preferences as to viewing. Some of these lids are compatible with only a sealed burial while others are compatible with only an unsealed burial. Some caskets are richly decorated while others are fashioned less lavishly. What is sought instead is a rich appearing viewing unit which permits wide variations in both the type of display and the type of burial.

Quite obviously, a casket unit versatile enough to be appropriate for all of the above situations should eliminate the added expense arising from the necessity of maintaining different casket lines for diiferent tastes. Such a unit should nevertheless be strong and durable, yet burn with little residue. The unit should be compatible with the type of display procedure which uses an attractively decorated lid capable of providing most of the various viewing variations but replaces this lid with an inexpensive unitary lid for burial or cremation. The unitary lid then provides a permanent seal against the environment or alternatively may be used without sealing. Means for inexpensive modification of the interior trim is also desirable, so that the casket may be used, as modified, in any religious ceremony. These advantages must be achieved at the lowest possible cost and weight without sacrifice of appearance.

Various attempts have been made to device casket units having sufiicient versatility to satisfy these requirements. A metal casket may be of impressive appearance but presents a problem in cremation because of the high temperatures required for oxidation and the metal slag produced. The high temperatures reached demand special refractories which are unavailable in the standard crematorium. Furthermore, metal caskets are extremely heavy (200 to 300 pounds, for example) and, therefore, are expensive to ship and difiicult to handle. Moreover, the metal casket is not proof against the elements and will in fact deteriorate with time.

3,406,229 Patented Oct. 15, 1968 Wooden caskets do not present the same problem with respect to cremation. However, wooden caskets are heavy, subject to deterioration, and do not appeal to the taste of the majority of people, although they are less expensive.

'Because of deficiencies of metallic and wooden caskets, attempts have been made to utilize various plastics in the production of lightand burnable, permanent caskets which may be produced economically, Heretofore, however, expensivematerials and manufacturing'techniques have' made the plastic caskets as expensive as metallic caskets without furnishing the attractive finish of the metallic caskets. Furthermore, the materials used in reinforced caskets leave a substantial residue of molten glass when burnt which may damage the refractory chamber of the crematorium. p q

Accordingly, it is an object of the present invention to provide an improved method of fabricating a casket unit which combines impressive appearance, strength and low weight with exceptional versatility.

Another object of the present invention is to improve the construction of casket units by a unique use of plastic materials.

A further object of the present invention is to reduce the expense of construction of casket units by utilizing improved manufacturing techniques and readily obtainable and inexpensive materials.

Yet another object of this invention is to provide an improved method of fabricatinga casket unit which has a number of different modes of use.

Briefly, the objects of this invention are accomplished by one exemplary casket unit comprising a body (termed a tub) and a lid, each of which may be formed of molded plastic sheet material in the form of outer and inner shells andhave a plastic foam material interposed between the shells. The resulting units are completely sealed, are durable, exhibit great strength, are light in weight, and burn at low temperatures with a minimum of residue. Furthermore, the tub and lid are formed to provide a unique arrangement which is suitable for either sealed or unsealed burials. In accordance with various features of the invention excellent structural characteristics are obtainedwith materials which usually are regarded as incompatible.

I Alternatively, a second exemplary casket unit may include a tub and lid each constructed of a molded plastic foam material having a strong and smooth outer surface which is formed by the foaming pressure itself. This second exemplary casket exhibits all of the desirable features of the first.

According to another aspect of the invention, as constructed by either method, the casket is fitted to receive highly decorated, removable, viewing lids and simple and inexpensive permanent lids. Temporary viewing lids are provided in accordance with the invention which are unique in allowing a number of different modes of viewing with a single lid. The temporary viewing lids also are so arranged as to allow different religious insertions to be interchanged so that the casket may be used for services of any faith.

Both the tub and lid manufactured according to either of the above-mentioned processes possess exteriors which may be painted to simulate a highly polished bronze or silver finish. Thus the casket is acceptable in any situation where the appearance of a metal casket might be desired. According to another aspect of the invention, a plastic sheet material having a leather-like grain surface may be used in the outer shells to provide a unique casket to realistically simulate a leather covering at very low cost.

These and other advantages and features of this invention will be better understood from the following detailed description, taken together with the drawings, in which like elements have likenesignations', and in which:

FIG. 1 is a perspective view of one form of casket arrangement in accordance with the present invention;

' FIG. 2a is a cross-sectional view illustrating constructional details ofthe arrangement of FIG.'1;

FIG. 2b is an enlarged view of a fragment of the arrangement of FIG. 2a;

FIG. 3 is a cross-sectional view illustrating constructional details of an alternative form of tub in accordance with the invention;

' FIG. 4 is a partial perspective view of a casket arrangement including a full length burial lid, shown in the raised position for conv enience'in describing the invention;

' FIG. 5 'is an enlarged view ofa fragment of a unique decorative device also illustrated in FIG. l; 7 FIG. 6 is a partial perspective view in accordance with the invention illustrating a unique convertible viewing lid for providing a variety of viewing arrangements; and

FIG.-7 is an enlarged perspective view of a hinge arrangement which may be employed in accordance with the invention.

Referring more particularly to the drawings, FIG. 1 illustrates a casket unit 10 which comprises a lid 11 and a tub 12 arranged in what is termed a couch or perfection couch viewing arrangement. Sets of handles 13 for lifting the casket unit 10 are affixed to the outer sides of the tub 12 by brackets 14. It should be noted that the side walls of the tub 12 may be slanted to distribute the lifting force so ,that a large weight may be supported without damage. The brackets 14 are attached to the tub 12 so that the handles 13 may be removed for cremation. Within the casket 10 are positioned conventional decorative supporting materials 16.

The viewing lid 11 shown in FIG. 1 includes a hinged portion 17 which may be pivoted upon a row of hinges (not shown in FIG. 1) for viewing and a closed portion 18 which covers the remainder of the casket 10. It should be noted that screw fasteners are provided for securely fastening the lid 11 to the tub 12.

In FIG. 2a there is shown a cross-section of the tub 12 and the lid 11 of the casket 10, illustrating various constructional features from which exceptional versatility isderived. The tub 12 comprises an inner shell 20, an outer shell 21 and an interposed material 22. The lid 11 (both portions thereof if a divided lid is utilized) may comprise an inner shell 23, an outer shell 24, and an interposed material 25. The shells 20, 21,. 23 and 24 may advantageously be constructed of a smooth-surfaced plastic sheet material such as polystyrene which may be molded at a relatively low temperature. The inner materials 22 and 25 may comprise a light weight plastic foam such as polyurethane foam which adds considerable strength without appreciably increasing the weight of the casket unit. Both of these materials burn at low temperatures with less residue than a comparable wooden casket and are therefore uniquely suitable for cremation. The plastic foam and sheet material are disposed, in a manner to be explained, in individual units which are completely sealed against the elements. As. has already been pointed out, prior attempts to utilize plastic materials in caskets have not been entirely successful because conventional resin formations reinforced with glass fibers burn but leave the fibers as a mass of molten residue in the refractory chamber. The plastic materials utilized in this invention are free from this disadvantage. The tub and lid arrangements shown in FIG. 2a are both manufactured in substantially the same .manner though in different shapes. For example, -the inner and outer shells 20 and 21 of the tub 12 are pre-formed to the desired shapes by well-known molding techniques such as the vacuum forming technique. In this technique a sheet of polystyrene material is heated and a vacuum is applied to draw it firmly into a female mold where it assumes the desired shape. The interior shell may have itscorners shaped in a manner such that they are not completely drawn out to a'point, as shown in FIG. 221. After molding, the inner and outer shells 20, 21 are held in spaced relationship to each other by suitable means such as guiding dies (not shown). The shells are spaced sufficient distances "apart to allow the liquid foam material to flow between them.

Before the plastic foam is poured, certain strengthening elementsmay'be placed between theshells 20, 21 and subsequently embedded andfixed within the plastic foam. For example, plastic blocks 26of a material such as acetal may be secured to the interior surface ofthe outer shell 21 to provide a means for positioning the brackets 14. The plastic blocks provide a reinforcing member for self-tapping screws which hold the brackets 14 against the outer surface of the tub 12. Thus, the brackets may be made removable for cremation. Various other means of support, such as wooden blocks, might also beprovided internally for positioning the brackets 14, and other members as well may be inserted between the shells before the foam material is inserted. For example, plastic members 27 may be secured within the lid to provide for retaining the upper member of a hinge arrangement which will be explained more fully below. The members 27 may advantageously have holes therein to allow the foam material to adhere more strongly. Additionally, strengthening members may be placed against the inner surface of the outer shell of the tub 12 for securing the lower portions of the hinging arrangements. Means, not shown, for reinforcing the screw fasteners 15 which hold the lid 11 to the tub 12 may also be positioned appropriately within the interior of the shells.

In the molding of the inner and outer shells of the tub and lid, a pair of mating surfaces (best seen in FIG. 2b) are formed which includean upper lip 28 extending from the inner shell 20 and a lower lip 29 extending from the outer shell 21. These lips contact around the entire periphery of the tub when the inner and outer shells are in final position. Before the foam material is poured, an adhesive may be placed upon the mating surface of one of the lips 28 or 29 to seal the shells together.

The liquid foam such as polyurethane, is poured into the bottom of the shell 20and catalyzed in a well-known manner so that after pouring it begins to foam. The inner shell is then placed in the appropriate position so that the lips 28 and 29 are in mating relationship and pressed together by the guiding dies. The liquid foam material foams up between the two shells and fills the inner surface.

In the fabrication of the tub and lid of the casket, air holes may be provided in one of the two mating lips 28 or 29, so that the air contained within the unfilled portion of the interior may be forced out during the foaming action. These holes will be sufficiently closed by the foam material as it fills the interior between the shells. The duration of the foaming action and the curing time for the adhesive applied between the lips 28 and 29 are selected to be substantially equivalent so that both are completed at approximately the same time. Upon the completion of the foaming and sealing actions, the tub is removed from the guiding dies for further finishing processes and for the attachment of the various fixtures.

It should be noted that in the normal situation a foam material such as polyurethane will attack and tend to decompose a sheet material such as polystyrene, forming blisters therein. Moreover,- if the materials are used to gether without provision for preventing such attack, they do not adhere. To provide against such an eventuality, the interior surfaces of the shells are coated with an acrylic lacquer bonding layer which protects the sheet material from attack by the foaming liquid and provides a surface (FIG. 2b) for the adherence of the foam to the shell material. Any commercially-available, solvent-thinned acrylic lacquer is suitable for this purpose.

As stated above, the lid 11 may be formed in a like manner to the tub by the use of appropriate molds and guiding arrangements. It should be noted, however, that the construction of this invention allows both a couch type lid, as shown in FIG. 1, and a full pa nel lid, as shown in FIG. 4, to be constructed from the same mold. In the manufacture, complete full length shells are provided. These-shells are cut into half sections for utilization in the couch arrangement. The portions at the cut are strengthened by providing cross-sectional elements which act to contain the foam. The foam material is then placed within the shellsin a manner substantially like that of the tub arrangement.

It should be especially noted that the fabrication o the lid may be. facilitated by a unique arrangement including an expandable bladder which is placed against the exterior of the inner shell during the foaming process. By filling the. bladder with a compressed gas, the inner shell is caused to press outwardly and assume the correct position againstthe outer shell forthe sealing operation. Thus, the lips of the inner and outer shells are maintained together during the curing of the adhesive material.

. Superior. strength may be obtained by pro-stressing the foam and the shells. This may be effected by heating, or maintaining the shells heated, as the foam is poured and hardens. The result is that on cooling the shells contract and press inwardly against the foam so that the various parts of the construction are held in a pre-stressed relationship, the foam being compressed and the polystyrene shells being in tension. As is well known, sheet material has great strength in tension while foam material has great strength in compression. Thus the outstanding properties of both materials are utilized to provide an especially strong casket.

-,An alternative construction of the lid 11 and the tub 12 which eliminates the inner and outer shells is shown in FIG. 3. A foam material '32, such as polyurethane, is poured into a mold having the requisite shape and hardens to form a tub or lid entirely of foam. While in the mold, the foaming action-exerts pressure to form a smooth and strong outer surface 33. The smooth exterior surface facilitates the application of a metallic lacquer which simulates bronze or silver metal effectively. Thus the construction shown in FIG. 3, as well as the construction shown in FIG- 2, may be finished to ahigh gloss which simulates bronze or silver metal (FIGJZb) and is exceedingly pleasing to the eye. Caskets. constructed according to this method are entirely acceptable in the place of the normal metallic casket. Alternatively, the resinsheet material used in the construction of FIG. 2 may have a patterned exterior surface, such as a leather-like surface, or may have a suitable color molded into the sheet material to eliminate the finishing step.

It should be noted that the resinmaterials utilized in the construction of the casket units disclosed herein are of a type which burn at a temperature substantially like that of wood. Thereforefthe caskets of this invention may be used for cremation in a standard crematorium. Further, the units of the casket are of inert synthetic materials which are entirely sealed, and the materials will not deteriorate if used to provide a'perrnanent burial repository.

It will be appreciated that any lid utilized for viewing will be substantially decorated and therefore expensive. Many of the standard viewing arrangements are sectionalized and therefore hard to seal to the tub. The caskets of this invention are constructed to accept a viewing lid as a temporary removable'portion and utilize a plain, inexpensive lid in burial or cremation in place of the decorative lid. Alternatively; various of the viewing lids may be utilized as desired in the burial .and are provided with sealing arrangements.

Heretofore, no simple arrangement for hinging a rc movable lid to a tub while providing a simple, permanent seal for a permanent lid has been suggested. The unique construction of the caskets of this invention furnishes such a simple arrangement. The inner shell of the tub 12 shown in FIG. 2b contains a downwardly-grooved channel 30in the upper periphery of the lip 28. In the construction of the inner shell 23 of a lid 11, a tongue 31 may be provided to extend downward and mate with the channel 30. In this manner, a tongue and groove assembly is formed in which a lid may be placed securely upon a tub either with or without sealing, as preferred.

An arrangement illustrating a full lid which may be of an inexpensive type for permanent sealingis shown in FIG. 4. It will be appreciated from the drawing that the tongue and groove structure eliminates any slippage between the tub and lid and facilitates the placement of the two, .strengthening the entire arrangement. Screwdown fasteners 15 at the corners of the lid 11 may be used for fastening the lid to the tub during shipping or for an unsealed burial. Alternatively, the lid may be permanently sealed to the tub simply by filling the channel 30 with a sealant 46 which has a highly viscous consistency at the time; when the lid is closed for sealing. Such a sealant will'partially fill the channel 30 and conform to the shape of the tongue 31, gripping the facing plastic surfaces in a complete hermetic and structural seal withoutthe aid of mechanical locking devices. A pliable mastic sealant which does not cure but remains in a pliable condition, such as a chromate, is a preferable sealant since it'may be placed in the channel 30 at any time, yet will not harden as will curing sealants. The use of such a sealant allows a substantial flexibility in manufacturing.

vEither one of two different techniques may be used in inserting the sealant. In one, illustrated in FIG. 4, the sealant 46 is placed in the bottom of the channel 30 and covered by a protective paper tape 47. The temporary viewing lid does not contact the sealant because of the paper tape 47, nor is the tape 47 seen by witnesses to the ceremony. The sealing compound 46 and the tape 47 may be provided in a roll for insertion by the mortician in the channel 30 at the appropriate time, or may be installed at the factory. The tape 47 may have a pressure sensitive surface along its edges, so that it rests firmly on the sides of the channel 30 in the tub 12. At the conclusion of the service, when the lid is to be sealed in place, the protective tape 47 is simply removed and the permanent lid is placed on the tub. If an unsealed burial is desired, the sealant may be left out of the groove; or, if provided at the factory, the tape may be left on so that no seal is effected.

In the other technique, the operator deposits the puttylike sealant from a tube within the channel 30 and places the lid 11 in position.

- Of especial note is the manner in which the molding arrangement allows the casket to be fabricated in a decorative manner. For example, the hinged viewing portion 17 of the lid 11 shown in FIG. 1, as well as other portions of the casket 10, may be provided with a roll 51 over which decorative material may be placed. The presence of the roll 51 raises the decorative material, giving it a full and luxuriant look without the use of expensive undercushioning. With the roll arrangement also, the decorative material may be placed within the casket at a minimum expense by simply stapling the under edges thereof to the plastic sheet material.

Another advantageous feature of the invention is the use of a decorative member or leaner 35, shown in FIG. 1 (covered by decorative material 37) and FIG. 5. The member 35 is a pad which covers the upper lip of the tub 12 and furnishes a soft yet firmly based surface for persons to rest upon in viewing the casket. The member 35 may be of a flexible foam material several inches thick and be extruded in a shape such as to fit around the upper edge of the lip and side of the tub 12, as shown, being secured by plastic resilient clips 36 which fit snugly about the lip of the tube 12. Appropriate decorative material 37 (FIG. 1) may be placed over the member 35. In use, pressure is applied downwardly upon the member 35 and the plastic clips 36 so that the clips 36 tighten about the 7 lip of the tub 12 and are not inadvertently moved by force applied from this direction. Upon the Completion of the religious ceremony or the viewing, the member may be readily removed and used again in other services, thereby reducing the cost of the funeral.

In FIGS. 2, 4, 6 and 7 is shown a unique hinging arrangement for mounting the temporary viewing lid 11 during the ceremony. Such an arrangement may also be provided for mounting the permanent lid. FIG. 4 shows the back of the casket 10, and a number of brackets 38 which are arranged at intervals along theouter surface of the shell 21 of the tub 12. A number of tongue members 39 are secured to the shell 23 of the lid 11 to mate with the brackets 38. The arrangement allows the lid 11 to be attached and raised for viewing and laterremoved without inconvenience.

In FIG. 7 is shown an enlarged view of a single hinge for securing the lid 11 to the tub 12. The hinge includes the bracket 38 which is connected to the tub 12 and has an outwardly extending portion 40 with an Opening of a shape to mate with the tongue member 39. The tongue member 39 is secured to the lid 11 and has a portion extending downwardly to fit through the opening of the bracket 38 with a curved portion 41 which extends outwardly against the bar of the portion 40 upon mating to provide a pivoting arrangement. It should be noted that the bracket 38 and the tongue member 39 have ho'es for securing them to the respective portions of the casket unit, such as by self-tapping screws, to allow for removal of the metallic members on cremation. As mentioned hereinbefore, reinforcing members such as members 27 and 34, shown in FIG. 2, may be embedded within the foam material for securing the screws of the hinge elements.

In FIG. 6 is shown a casket including a convertible lid 11. The lid 11 includes a fixed portion 18 and a viewing portion 17 having a panel 42. The panel 42 is shown in a raised position for viewing, supported by a hinging arrangement including a collapsible retaining member 43. In the closed position the panel 42 has a screw fastener 44 positioned to fit into a tapped hole 45 of the viewing portion 17 in a well known fashion for holding the viewing panel 42 tightly to the portion 17. When the panel 42 is used for viewing, the portions 17 and 18 are secured in a like manner to the tub 12 by screw fasteners 15, as explained above. Alternatively, the panel 42 may be secured to the portion 17 and that portion 17 utilized for viewing in the couch arrangement shown in FIG. 1.

The viewing lid shown in FIG. 6 is constructed in a different manner than the lids described before. For example, the convertible lid may be constructed of a fiber glass material. The convertible lid arrangement is intended to be a temporary removable item which may be purchased by the mortician and utilized in a number of ceremonies in a manner depending on the desires of the parties involved. Since the lid is reusable it may be more extravagantly and luxuriantly decorated than other arrangements and may include materials which do not burn well. The temporary viewing lid of the convertible type is normally provided without a tongue member so that it may be utilized without any interference with the sealant placed within the channel 30 of the tub 12.

A consideration of the various aspects and features of this invention demonstrates the versatility of the construction and the various viewing lids. For example, the convertible lid may have the viewing panel 42 screwed down securely to provide a couch type of arrangement. On the other hand, the portion 17 of the lid may be secured to the tub 12 and the panel 42 left open so that a panel arrangement is formed. Or, as desired, a full panel arrangement may be utilized- "for vie'wingwith the same tub. When secured to the tub by the hinging a rrangement disclosed herein, any viewing lid may be conveniently removed and a permanent lid placed on the casket for burial or cremation.==It will be appreciated that the temporary lidin no way interferes with the permanent sealing arrangement practiced inathe final disposal but only allows the ceremony to take place with a more attractive viewing lid at a decreased expense. Furthermore, the novel sealing arrangement allows, in conjunction with the fasteners 15, either sealed or unsealed burials. 1

Although particular casket units have been described above by wayof example of the manner in which various aspects of the invention may be used to advantage, it will be appreciated that the invention is not limited thereto. Accordingly, any and all modifications, alterations and equivalent arrangements falling Within the scope of the following claims should be considered to be apart of the invention. I I

What is claimed is: 4

1. In a method of manufacturing a casket unit, the steps comprising:

vacuum forming an inner shell from polystyrene sheet material, the inner shell including a convex outer surface and amating surface; vacuum forming an outer shell, larger than the inner shell, from polystyrene sheet material, the outer shell including a concave inner surface and a mating surface;

coating the outer surface of the inner shell and the inner surface of the outer shell with an acrylic lacquer; applying a 1 charge of polyurethane foam-forming agents onto the inner surface of the outer shell;

positioning the inner shell within the outer shell, in spaced-apartrelation, with the outer surface of the inner shellfacing the inner surface of the outer shell, the polyurethane foamforming within the space between the shells, the charge of foam-forming agents being sufiicient to form a quantity of polyurethane foam 'which substantially fills the space between the shells; and

adhering together. the mating surfaces of the shells to close the space between the shells.

2. The method of manufacture as in claim 1 further comprising the step of heating said shells before the foam material is poured therebetween to. cause a prestressed relationship between the shells and the foam material upon cooling, .with the foam material being under compression and the shells under tension.

References Cited .Moroni et al. 264-48 JAMES A. SEIDLECK, Primary Examiner.

P. E. ANDERSON, Assistant Examiner. 

1. IN A METHOD OF MANUFACTURING A CASKET UNIT, THE STEPS COMPRISING: VACUUM FORMING AN INNER SHELL FROM POLYSTYRENE SHEET MATERIAL, THE INNER SHELL INCLUDING A CONVEX OUTER SURFACE AND A MATING SURFACE; VACUUM FORMING AN OUTER SHELL, LARGER THAN THE INNER SHELL, FROM POLYSTYRENE SHEET MATERIAL, THE OUTER SHELL INCLUDING A CONCAVE INNER SURFACE AND A MATING SURFACE; COATING THE OUTER SURFACE OF THE INNER SHELL WITH AN ACRYLIC INNER SURFACE OF THE OUTER SHELL WITH AN ACRYLIC LACQUER; APPLYING A CHARGE OF POLYURETHANE FOAM-FORMING AGENTS ONTO THE INNER SURFACE OF THE OUTER SHELL; POSITIONING THE INNER SHELL WITHIN THE OUTER SHELL, IN SPACED-APART RELATION, WITH THE OUTER SURFACE OF THE INNER SHELL FACING THE INNER SURFACE OF THE OUTER SHELL, THE POLYURETHANE FOAM FORMING WITHIN THE SPACE BETWEEN THE SHELLS, THE CHARGE OF FOAM-FORMING AGENTS BEING SUFFICIENT TO FORM A QUANTITY OF POLYURETHANE FOAM WHICH SUBSTANTIALLY FILLS THE SPACE BETWEEN THE SHELLS; AND ADHERING TOGETHER THE MATING SURFACES OF THE SHELLS TO CLOSE THE SPACE BETWEEN THE SHELLS. 